A general investigation was made of the coexistence relationships of n+1 phases in the isothermic‐isobaric sections of n‐component systems. It was found that for a given set of n+1 phases there are at most only two coexistence patterns possible. As a result in n‐component systems, as well as in ternary systems, theoretically only a single well‐chosen sample has to be examined for the phases it contains in order to completely clarify the phase coexistence relationships of n+1 phases whose composition is already known. The results obtained were further used to develop a general classification of the types of non‐variant equilibria occurring in many component systems.

A photo‐tube method for measuring the concentration of ozone is described. Measurements were made of the rate of production and rate of decomposition of ozone in oxygen and in air by low pressuremercury vapor lamps. The production in oxygen is enhanced by the presence of nitrogen. Increasing the moisture content of the gas decreases the rate of production and increases the rate of decomposition. A new germicidal lamp enclosed in a 10‐liter glass tube will form an equilibrium concentration of 145 parts per million by volume. A quartz lamp under the same conditions will form 640 parts per million. With oxygen flowing through the tube the yield for the quartz lamp is 2.5×10−3 g ozone/min. or 10 g kw hr.

Solutions are given for the free flexural vibration of a cylinder vibrating as a rod would vibrate and for the free flexural vibration of a disk vibrating as a circular plate would vibrate. The solutions are based upon the mathematical theory of elasticity. Curves are given showing the correction factors which, when applied to the elementary solutions, will give results in agreement with those obtained by means of the more rigorous solutions given here.

A method for attaining high dispersion in electron diffraction is presented. High dispersion may be obtained by primary magnification of a diffraction pattern formed in the normal manner at the object plane of a magnetic or electrostatic lens. Dispersion may be varied continuously by changing the lens current or voltage. The design of diffraction cameras of this type is discussed and their value in diffraction problems pointed out. The validity of the method is established by diffraction patterns obtained using a modified electron microscope adapter.

Experimental investigations of the strain hardening of metals under combined stresses are usually conducted so that the directions of the principal stresses as well as the ratios of their magnitudes remain constant during any one test. The paper is concerned with incompressible isotropic materials which are stressed in this manner and deform in accordance with certain postulates. The most general stress‐strain relation which can arise under these circumstances is established, and some special cases of this relation are discussed.

A coil system is described which produces very constant magnetic gradients throughout a considerable part of the volume occupied by the coil assembly. One modification produces constant transverse and longitudinal gradients of the field transverse to a long cylindrical region; another modification produces constant transverse and longitudinal gradients of the magnetic field throughout a spherical volume. Gradient data are given for both modifications.